Peter Ford had sparked outrage earlier this month when he claimed in a BBC interview that Assad would not have carried out the chemical gas attack on his own people.

According to the British newspaper, only weeks before the 4 April chemical massacre on the Syrian village of Khan Sheikhoun that killed over 100 people, Ford was appointed the director of the British Syrian Society.

The controversial lobby group was founded by Fawaz Akhras, a London-based cardiologist whose daughter Asma is married to Assad, frequently accused of acting as its mouthpiece in the West.

It has been the subject of criticism and controversy in recent years over its role in providing support for Assad, with a string of senior British figures resigning from its board.

The group was also accused of running a propaganda event in Damascus that was supported by Syrian government officials.

In September 2011, the HSBC bank said it would no longer represent the society.

One week after the chemical attack, which triggered retaliatory US airstrikes on a regime airbase, Ford appeared on the BBC saying it was out of character for the Syrian president to provoke US President Donald Trump, just as Washington was taking a softer line compared to Barack Obama's policies on Syria.

"Assad may be cruel, brutal, but he is not mad," said the former ambassador, who served in Damascus from 2003 to 2006.

"It defies belief that he would bring all this on his head. For no military advantage. The site that was hit had no military significance. It made absolutely no sense. It would have angered the Russians for no other reason: it was simply not plausible."

The BBC has defended using Ford as a commentator on events in Syria.

"When Peter Ford has appeared on various BBC outlets this year his particular viewpoint has been signposted in the introduction in terms the audience will understand, for example he has been variously described as a 'long term critic of Western Policy', or part of 'a dwindling group who still think Bashar al-Assad is the solution to Syria'," a spokesperson said.